Measurement of angular momentum flux in optical tweezers

Halina Rubinsztein-Dunlop; Theodor Asavei; Daryl Preece; Alexander B. Stilgoe; Norman R. Heckenberg; Timo A. Nieminen

doi:10.1117/12.886221

16 February 2011 Measurement of angular momentum flux in optical tweezers

Halina Rubinsztein-Dunlop, Theodor Asavei, Daryl Preece, Alexander B. Stilgoe, Norman R. Heckenberg, Timo A. Nieminen

Proceedings Volume 7950, Complex Light and Optical Forces V; 79500I (2011) https://doi.org/10.1117/12.886221
Event: SPIE OPTO, 2011, San Francisco, California, United States

Abstract

It is well established that a light beam can carry angular momentum and therefore when using optical tweezers it is possible to exert torques to twist or rotate microscopic objects. Both spin and orbital angular momentum can be transferred. This transfer can be achieved using birefringent particles exposed to a Gaussian circularly polarized beam. In this case, a transfer of spin angular momentum will occur. The change in spin, and hence the torque, can be readily measured optically. On the other hand, it is much more challenging to measure orbital angular momentum and torque. Laguerre-Gauss mode decomposition, as used for orbital angular momentum encoding for quantum communication, and rotational frequency shift can be used, and are effective methods in a macro-environment. However, the situation becomes more complicated when a measurement is done on microscale, especially with highly focused laser beams. We review the methods for the measurement of the angular momentum of light in optical tweezers, and the challenges faced when measuring orbital angular momentum. We also demonstrate one possible simple method for a quantitative measurement of the orbital angular momentum in optical tweezers.

Citation Download Citation

Halina Rubinsztein-Dunlop, Theodor Asavei, Daryl Preece, Alexander B. Stilgoe, Norman R. Heckenberg, and Timo A. Nieminen "Measurement of angular momentum flux in optical tweezers", Proc. SPIE 7950, Complex Light and Optical Forces V, 79500I (16 February 2011); https://doi.org/10.1117/12.886221

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